This often includes chemical sprays and multiple cycles of acid-washing, the toxic runoff can turn rivers indigo-blue.

这通常包括化学喷雾和多次酸洗循环，有毒的径流会使河流变成靛蓝色。

So in that 500 million years, they survived multiple natural cycles of warming, and multiple natural cycles of cooling.

所以在这 5 亿年里，它们经历了多次自然变暖、自然降温周期。

I don't mind winter-that's when Orion is visible, and astronomical delights abound during the long, dark nights-but I also know that there are multiple and subtle cycles at work all the time.

我不介意冬天——那时猎户座是可见的，在漫长、漆黑的夜晚里，天文的乐趣比比皆是——但我也知道，一直有多种微妙的周期在起作用。